Antifriction roller bearing

ABSTRACT

An antifriction roller bearing, in which two sets of units are arranged so as to face each other in an one-axis direction. Each unit comprises an inner ring, an outer ring and rollers, the inner and outer rings being provided respectively with a raceway track of mono-hyperboloid of revolution about the one axis. The rollers are arranged so as to come into linear contact with the inner and outer raceway tracks and slant to a plane including the one axis at an angle. An energizing means is arranged between both the inner rings or both the outer rings to energize the inner rings or the outer rings so as to narrow down the spacing of the raceway tracks, the outer rings or the inner rings which are not subject to the energizing force being stationary.

INDUSTRIAL FIELD OF APPLICATION

This invention relates to an antifriction roller bearing which canrotate only in one direction.

PRIOR ART

In general, antifriction roller bearings includes the three types ofcylindrical roller bearing, conical roller bearing and self-aligningroller bearing.

With the cylindrical roller bearings, the rollers are in line contactwith the inner and outer rings, and a radial load applied on the bearingproduces only normal loads on the contact portions.

On the other hand, with the conical roller bearings and theself-aligning roller bearings, a radial load produces a normal loadacting vertically on the slanted surface and a tangential load acting inparallel to the slanting surface. But, since a thrust load is alwaysapplied to those bearings to prevent the inner and outer rings fromdisplacing in the axial direction, an additional normal component of thethrust force are applied vertically between the rings and rollers, thusproducing an additional surface contact pressure. Further, since thenormal load acting between the rings and rollers tends to push therollers out of the raceway from smaller dia. side to larger side, theguide flange must be provided at the larger dia. side to prevent therollers from being driven out of raceway. But, since the large-dia. endface of the conical rollers is in sliding contact with the guide flange,the PV value contributed by the sliding friction largely restricts theload carrying capacity of the conical type roller bearings.

Problems to be Solved by the Invention

The antifriction roller bearings are often used where a shaft or ajournal is rotated in both normal and reverse directions, but, dependingon the type of machinery, sometimes used where a shaft or a journal isrotated only in one direction.

The present invention intends to provide an antifriction roller bearingwhich can be widely used in a variety of machinery, with a larger loadcapacity than the conventional cylindrical and conical roller bearingsand an enhanced rolling performance without producing such a largesliding friction at the large-dia. end face of the rollers asexperienced in the conical roller bearing, as well as has a highefficiency of power transmission performance without any possibility ofbearing seizure, thus most suitable for high speed rotation.

Means for Solving the Problems

To solve the above problems, an antifriction roller bearing according tothe present invention comprises:

two sets of bearing single units each consisting of an inner ring, anouter ring and intermediate rotation bodies, and one set of energizingmeans; and

the inner ring being provided with an inner raceway track ofmono-hyperboloid of revolution about one axis;

the outer ring being provided with an outer raceway track ofmono-hyperboloid of revolution about the axis;

the inner raceway track and the outer raceway track being oppositelyfaced with each other to form a raceway whose diameter is larger at oneend than at the other end;

the center axes of the intermediate rotation bodies with a cylindricalor conical rolling surface being arranged in a circumferential directionof the raceway at an angle to a cross section including the axis, andthe surface of the intermediate rotation bodies being arranged so as tocome into linear contact with the inner raceway track and the outerraceway track;

the inner ring or the outer ring rotating only in such a given directionas to roll the intermediate rotation bodies along the inner racewaytrack in the one-axis direction toward a small-dia. end of the raceway;

the inner ring or the outer ring being provided with a ringlike portionwhich brings to a stop movement of the intermediate rotation bodies inthe axial direction, when the inner ring or the outer ring is rotated inthe given direction;

the two single units being arranged so as to face each other in theone-axis direction;

the energizing means being arranged between the inner rings or the outerrings faced each other in the one-axis direction, to energize the innerrings or the outer rings in the axial direction so as to narrow down thespacing of the raceway tracks; and

the outer rings or the inner rings which are not energized by theenergizing means being stationary so as not to displace in the axialdirection.

Operation

Since both the inner and outer raceway tracks are formed ofmono-hyperboloids of revolution, the raceway formed of these tracks hasa diameter larger at one axial end side than at the other end. Further,since the intermediate rotation bodies are disposed slanted to sectionsincluding the center axis of the bearing, when the inner (or outer)rings are rotated, the intermediate rotation bodies will not only rollon the inner and outer ring raceway tracks while keeping line contactwith them and being guided by them, but also will tend to advance in theaxial direction. But, since the senses of the advancements of theintermediate rotation bodies at the inner and outer raceway tracks areopposite to each other, the inner rings and the outer rings would beseparated away from each other in the axial direction by theintermediate rotation bodies.

In this case, since the inner rings (or the outer rings) are to berotated in a given direction which will cause the intermediate rotationbodies to be moved on the inner ring raceway trakcs toward the smallerdiameter ends, the above separation force tends to move the inner ringsto the larger diameter ends of the raceway, and the outer rings to thesmaller diameter ends, thus invariably resulting in a generation of anaction which tends to widen the gap of the raceway.

On the other hand, the bearing single units each including the inner andouter ring and the intermediate rotation bodies are disposed opposite toeach other in the axial direction, and one pair of the outer rings (orthe inner rings) facing each other are fixed together to a bearingassembly case with the other pair being energized in the axial directionby the energizing means so as to narrow down a gap of the raceway.Therefore, the above separation force cannot remove away the inner ringsand outer rings from each other, resulting in a rotation of theintermediate rotation bodies floating on the raceway tracks while theinner rings (or the outer rings) are being subjected to a separationforce from one sense and an energizing force from the other oppositesense.

Such being the case, the intermediate rotation bodies would be subjectedto forces each in opposite senses of the axial direction from the innerand outer rings as a reaction of a force by which the inner and outerrings tend to be separated away from each other. If the magnitudes ofthe opposite forces are different, the intermediate rotation bodies maytend to move in the axial direction. When the intermediate rotationbodies are of conical shape, they may be subjected to an additionalforce pushing out them from the smaller dia. end side to the larger dia.end side, thus resulting in an axial movement depending on which islarger. The ringlike portions or the flanges on the inner rings end orthe outer ring end are provided to bring such a movement of theintermediate rotation bodies to a stop in position, thus preventing theintermediate rotation bodies from being driven away from the raceway.

Next, the magnitude of the above separation force produced on thecontact line of the intermediate rotation bodies with the inner andouter rings depends on the contact condition. In other words, sinceconvexed portions of the intermediate rotation bodies contact withconvexed portions of the inner rings while they contact with concavedportions of the outer rings, a contact surface pressure produced when aradial load is applied on the bearing assembly may be larger in the sideof the inner raceway track, thus producing a larger separation force onthe inner raceway track side. As a result, with intermediate rotationbodies of cylindrical shape, the differential separation force causesthe intermediate rotation bodies to slide in the axial direction againstthe ringlike flange and stop there, thus resulting in the differentialforce acting between the intermediate rotation bodies and the flanges ascontact surface pressure. But, this differential pressure is not solarge that frictions at the contact portions cannot be a problem.

On the other hand, with intermediate rotation bodies of conical shape,as described previously, the intermediate rotation bodies are subjectedto a push-out force caused by the pressure at the contact portions. But,the contact pressure is reduced by the separation force, and further thedifferential separation force acts in an opposite direction to that ofthe push-out force. Therefore, no large contact surface pressure may beproduced between the intermediate rotation bodies and the ringlikeflanges.

BRIEF DESCRIPTION OF THE DRAWINGS

Now preferable embodiments of the antifriction roller bearing accordingto the present invention will be described, referring to theaccompanying drawing (FIGS. 1 to 11):

FIG. 1 is a sectional view showing an embodiment of the antifrictionroller bearing according to the present invention;

FIGS. 2 and 3 are perspective views showing the arrangement of the maincomponents and the rollers in the above embodiments;

FIGS. 4 and 5 are schematic diagrams showing the relation of forcesacting in the antifriction roller bearing;

FIG. 6 is a sectional view showing another embodiment of theantifriction roller bearing according to the invention;

FIGS. 7 to 9 are schematic diagrams showing how to determine the racewaytrack surface shape of the embodiment shown in FIG. 6;

FIG. 10 is a sectional view showing a separate embodiment of theantifriction roller bearing according to the invention; and

FIG. 11 shows how forces act on the rollers in the embodiment shown inFIG. 10.

EMBODIMENTS

First, the configuration of an antifriction roller bearing according tothe present invention will be described using the sectional andperspective views shown in FIGS. 1 to 3.

In the drawings: A single unit 20 (or 20') of an antifriction rollerbearing includes an inner ring 1 (or 1'), an outer ring 2 (or 2') andintermediate rotation bodies or rollers 3 (or 3'). This antifrictionroller bearing assembly according to the invention consist at least ofone set of the two single units 20 and 20' disposed facing each other.Since the two units are of the same configuration, the single unit 20will be described in detail.

The inner ring 1 may be mounted on a shaft 4 by key 5 engagement. Aninner raceway track 1a and an outer raceway track 2a form a raceway 8for the rollers 3.

A plurality of the rollers 3 embodying an intermediate rotation bodiesare of cylindrical shape, and as shown in FIG. 3, are so disposed in theraceway 8 that they slant to a plane including a central axis 6 of theinner ring 1 at angle β(e.g., 15°).

A spring 7 used for energizing means is disposed in between the innerrings 1, 1', to push away them all the time so as to narrow a gap of theraceway 8 or separate away the inner rings 1, 1' from each other.

The inner ring 1 is provided with a ringlike flange 9, to restrict anaxial movement of the rollers 3 when the inner ring 1 is rotating andthe rollers 3 rotates about their own axes to advance in the axialdirection 6. The flange 9 may be provided on the outer ring 2.

In FIG. 3, the rollers 3 are disposed on the inner ring 1 slanting to aplane including a central axis 6 of the inner ring 1 at angle β. Eachposition of the rollers 3 is maintained by a retainer 10, thus avoidingtheir contact with each another. This configuration can prevent adjacentrollers rotating about their own axes in the same direction from runningagainst each another with opposite tangential velocities, thus resultingin their smooth rotations about their own axes and on the inner ringraceway track 1a.

With the antifriction roller bearing assembly, the shaft 4 is rotatedinvariably to a given direction, that is, in FIG. 2, in the clockwisedirection viewed from the right side (in the direction of arrow A). Whenthe shaft 4 rotates the inner ring 1 in A direction, the rollers 3 areguided by the inner ring raceway 1a while keep line contact with theinner ring raceway track 1a, to rotate about their own axescounterclockwise (in the B direction) and advance toward the left sidein FIG. 2.

On the other hand, when the rollers 3 rotate in the B direction, therollers 3 tend to advance to the right side, guided by the outer racewaytrack 2a while maintaining a line contact with the outer raceway track2a.

FIG. 4 is a schematic diagram showing forces acting between the rollers3 and the inner and outer rings 1 and 2 caused by such movement of therollers 3 as described above:

Each of the rollers 3 makes a linear contact (strictly speaking, a planecontact with a small width) with the inner and outer raceway tracks 1aand 2a. For simplification, consider contact points A and B on thecontact planes. Since the axis 3a of a roller 3 is arranged slanting toa section including the shaft axis 6 by an angle of β, the roller'srotational direction S has a slant angle of β relative to directions Ttangential to the raceways 1a and 2a. Therefore, when the rollers 3 arerotating on the raceways 1a and 2a, as shown in FIG. 3, the inner andouter rings 1, 2 would be applied by tangential force components Ti andTo and axial force components Ri and Ro.

The axial forces Ri and Ro may tend to separate the inner and outerrings 1 and 2 away from each other in opposite senses of the axialdirection of the shaft 4. With this embodiment in which the position ofthe outer ring 2 is stationary, the inner ring 1 may tend to move to theright in FIGS. 1 and 2, so as to widen the gap of the raceways 8.

Such forces acting on the inner and outer rings 1 and 2 produces abalanced energizing force of the spring 7, thus causing the rollers 3 tofloat on the inner and outer rings 1 and 2, leading not only to areduction of rolling contact surface pressure but also to a preventionof such troubles as smearing, galling and hardening of the surfaces inthe overload condition.

As for the surface contact of the rollers with the inner and outer rings1 and 2, as shown in FIG. 5, a convexed portion of a roller 3 contactswith a concaved portion of the outer ring raceway track surface 2a,while a convexed portion of a roller 3 contacts with a convexed portionof the inner ring raceway track surface 1a. As a result, a maximumcontact surface pressure Pi on the inner ring 1 is larger than a maximumcontact surface pressure Po on the outer ring 2. Therefore, in thecontact portions of the rollers 3 with the inner and outer rings 1 and2, the inner ring 1 causes a larger local concentrated strain than theouter ring 2. As a result, when the rollers 3 are rotating whileapplying a same normal force N on the inner and outer rings 1 and 2, aforce component Ri of the rollers 3 tending to move the inner ring 1 inthe axial direction is larger than a force component Ro of the rollers 3tending to move the outer ring 2.

As reactions of such force components Ri and Ro, the rollers 3 would besubjected to forces -Ri and -Ro from the inner and outer rings 1 and 2which are equal to Ri and Ro in magnitude and opposite in direction. Asa result, the rollers 3 tend to advance to the left side (in FIGS. 1 and2) in the central axis 6 direction while guided by the inner ringraceway track 1a. In order to stop such a movement of the rollers 3, theringlike flange 9 is provided on the inner ring 1 end portion asdescribed previously.

In this case, the end faces of the rollers 3 come into sliding contactwith the flange 9 while rotating about their own axes and in the raceway8, but the contact force equals (Ri-Ro), thus remaining a small value,so that this sliding friction causes no significant troubles on thebearing.

Accordingly, this antifriction roller bearing according to the inventioncan solve such problems experienced in the conventional conical rollerbearings, as seizures in the high speed rotation due to excessive PVvalue of the guide flange and failures associated with poor lubrication.Further, the minimized sliding friction loss and the capability of highspeed rotation significantly reduce the mechanical loss of the bearing,thus leading to a substantial improvement of bearing efficiency.

FIG. 6 is a sectional view showing another embodiment of theantifriction roller bearing according to the invention:

With the above antifriction roller bearing, the inner ring 1 is fixed onthe shaft 4 to prevent an axial displacement of the inner ring 1, whilethe outer ring 2 can move in the axial direction with the spring 7provided in between the outer rings 2 and 2'.

Therefore, when the shaft 4 is rotated in one given direction, therollers 3 and 3' also rotate guided by the inner rollers 1 and 1', thuscausing the outer rings 2 and 2' to approach each other so as to widenthe raceway gap. As a result, the rollers 3 and 3' will float on theinner rings 1 and 1' and in the outer rings 2 and 2', thus alleviatingcontact surface pressures between them. With respect to the otherpoints, the configuration and function of the antifriction rollerbearing are all the same as the one shown in FIG. 1, thus omittingfurther descriptions.

Now, shapes of the inner and outer ring raceway tracks 1a and 2arequired for the line contact of the rollers 3 with them will bedescribed as follows:

FIGS. 7 to 9 are explanatory drawings for determining the raceway tracksurface shapes in the case of cylindrical rollers 3.

FIG. 7 is a perspective view showing X-Y-Z coordinates, in which aroller 3 is so placed that its axis 3a passes through the Y axis adistance F away from the origin O, in parallel to the X-Z plane,slanting to the X-Y plane at an angle of β. The X axis represent thecommon axis 6 of the inner and outer rings 1 and 2. The section 3b ofthe roller 3 shows a section cut by a parallel plane to the Y-Z planepassing the X axis at an arbitrary position x. Points Uc and U'c arerespectively intersections with the X axis and the X-Z plane, ofperpendiculars drawn from the center Pc of the cross section to the Xaxis and the X-Z plane. The line 3a' passing the origin O and the pointU'c is a projected line of the roller axis 3a to the X-Z plane, formingan angle β with the X axis. Apparently referring to FIG. 7,

Distance from Uc to U'c=x tan β

Distance from Pc to U'c=F

Therefore, designating a distance from the rotation axis 6 of the rings(or X axis) to the center Pc of the roller 3 as yc (=PcUc),

    yc.sup.2 =F.sup.2 +(x tan β).sup.2

Accordingly,

    yc.sup.2 /F.sup.2 -x.sup.2 /(F/ tan β).sup.2 =1       (1)

Since the equation (1) is a hyperbola, the axis line of the rollers 3,that is, the center line of the raceway formed with the inner and outerrings 1 and 2 is hyperbolic with respect to the rotation axis 6 of therings.

FIG. 8 is a drawing for explaining how the rings 1 and 2 come intocontact with the roller 3 arranged as above.

Designate as Q an intersection of the axis X with a plane which passesthe center Pc of the roller 3 at right angle with the axis 3a of theroller 3. Considering spheres Si and So (only So is shown in FIG. 8)having the same center Q, which are respectively inscribed andcircumscribed to the rollers, contact points Pi and Po of the roller 3with the spheres Si and So would be on a perpendicular connecting thepoints Q and Pc, respectively the radius r of the roller 3 apart fromthe point Pc. Therefore, designating the distance from point Q to pointPc as R, the radii of the spheres Si and So would be respectively (R-r)and (R+r).

Designating as Ui and Uo the intersections of planes passing the pointsPi and Po in parallel to the Y-Z plane with the X axis (see FIG. 9), thelengths yi and yo of the segments PiUi and PoUo are respectivelydistances from the points Pi and Po to the X axis, and the distances xiand xo from the origin O to the points Ui and Uo are respectively the Xaxis coordinates of the points Pi and Po. Therefore, functions F (xi,yi) and F (xo, yo) represent the curved surface shapes of the racewaytracks 1a and 2a of the inner and outer rings 1 and 2.

FIG. 9 is an enlarged view showing related portions to the determinationof these functions.

Since segment QPc (equal to R) is at right angle with the center axis 3aof the roller 3, and the point U'c is an intersection of theperpendicular from the point Pc to the X-Z plane therewith, segment U'cQis at right angle with the axis 3a'. Therefore,

Distance from point O to point Q ##EQU1##

Then, designating an angle QPcUc as φ, since triangle QPcUc is a rightangle, ##EQU2##

On the other hand, since the length of segments PcPi and PcPo equal r,and triangles QPiUi and QPoUo are similar to triangle QPcUc, ##EQU3##

From these above equations, F (xi, yi) and F (xo, yo) are introduced asfollows: ##EQU4##

These equations express only that the inner and outer raceway tracks 1aand 2a have shapes of quadratic curved surface. Obtaining ratios of(xi-x)/(yi-yc) and (xo-x)/(yo-yc), from the equations (2) to (5),##EQU5##

Since the relation of x and yc is hyperbolic from the equation (1), andtan² β in the above equations is constant, the relations of xi and yi aswell as xo and yo are hyperbolic. As a result, the inner and outerraceway tracks 1a and 2a are mono-hyperboloids of revolution about thecommon axis 6.

Assuming for example

    yi.sup.2 /ai.sup.2 -xi.sup.2 /bi.sup.2 =1

    yo.sup.2 /ao.sup.2 -xo.sup.2 /bo.sup.2 =1

F=9, r=1.5, and β=15°, ai, bi, ao and bo are respectively calculated tobe 7.5, 30.7, 10.5 and 36.2, thus giving the inner and outer racewaytrack surfaces as mono-hyperboloid.

Next, an antifriction roller bearing assembly in which the bearingsingle unit has an intermediate rotation bodies with a conical shape ofrollers will be described:

FIG. 10 is a sectional view showing an embodiment of the aboveantifriction roller bearing assembly, corresponding to FIG. 1. Theassembly is different from the one in FIG. 1 only in that the rollers 3and 3' are of conical shape instead of cylindrical shape.

When the conical rollers are used, rolling performance of the assemblyis further enhanced.

As compared to the common cylindrical roller bearings, the conicalroller bearings generally involve the problem of large sliding frictionat the larger diameter sides of the rollers, but this antifrictionroller bearing assembly according to the invention solved this problem.

This solution will be described referring to FIG. 11. FIG. 11 is aschematic diagram showing how forces act on the rollers in theembodiment shown in FIG. 10.

As described previously, the rollers 3 and 3' are subjected to the axialcomponents of forces -Ri and -Ro from the inner and outer rings 1 and 2.Since Ri>Ro, as shown in FIG. 11, the roller 3 is subjected to an axialcomponent of force (Ri'-Ro') which tends to displace the roller in theaxial direction toward the small diameter end. Further, since the roller3 is of conical shape, as shown in FIG. 11, the roller 3 is subjected toan axial component U of normal forces N acting on the contact surface,which tends to displace the roller in the axial direction toward thelarge diameter end.

As described above, the roller 3 may slide toward the smaller or largerdiameter end, depending on which is larger, force (Ri'-Ro') or U. And, aringlike flange 9 is provided on the side of the inner ring 1 or theouter ring 2 toward which the roller 3 may displace. With the embodimentshown in FIG. 10, an assumption of (Ri'-Ro')>U is made, thus providingthe flange 9 on the roller's small diameter side end of the inner ring1.

As described above, with the conical roller bearing according to theinvention, the large pull-out force U acting on the large diameter sideend of the roller 3 in the conical roller bearing according to the priorart is substantially reduced, thus permitting only an auxiliary flangeto be provided on the large (or small) diameter end side of the roller3, resulting in a smaller PV value due to the sliding friction whichwill not restrict the load carrying capability of the bearing.

Since the generator of conical roller is a slanting line, the shapes ofthe inner and outer ring raceway tracks in the conical roller bearingare also of mono-hyperboloid of revolution like the cylindrical roller,but the hyperboloid is slanted by the slope of the conical generator.

In this connection, the bearing in FIG. 10 has a configurationcorresponding to the one in FIG. 1, but may has a configurationcorresponding to the one in FIG. 6.

Further, with the above embodiments, the shaft 4 is connected to a powersystem and rotated with the inner rings 1. But, alternatively, the bossside (not shown) and the outer rings 2 may be rotated.

Furthermore, in the above embodiments the intermediate rotation body isof a cylindrical or conical shape, but an hour-glass or convenxed drumshape may be used.

When a roller surface is of an hour-glass shape which is formed byrevolving a part of ellipse about an outside axis, the inner ringsurface is made into a cylindrical shape while the outer ring surface ismade into a curved surface formed by combining an ellipsoid ofrevolution and a hyperboloid of revolution. When a roller surface is ofa convexed drum shape which is formed by revolving a part of ellipseabout its center axis, the outer ring surface is made into a cylindricalshape while the inner ring surface is made into a curved surface formedby combining an ellipsoid of revolution and a hyperboloid of revolution.

Effect

As described above in detail, with the antifriction roller bearingaccording to the present invention:

The intermediate rotation bodies are arranged slanted to the inner andouter rings so as to have a line contact with the raceway tracks, theinner and outer rings are separated away so as to have the intermediaterotation bodies float from them, and the axial movements of theintermediate rotation bodies are uniformed. Therefore, the antifrictionroller bearing according to the invention can improve the bearing loadcarrying capability and the rolling performance, thus minimizing thesliding friction, resulting in not only prevention of the occurrence offailures associated with seizure or poor lubrication, but also a highbearing efficiency most suitable for high speed rotation.

What is claimed is:
 1. An antifriction roller bearing comprising:twosets of single units each consisting of an inner ring, an outer ring andintermediate rotation bodies, and one set of energizing means; and saidinner ring being provided with an inner raceway track ofmono-hyperboloid of revolution about one axis; said outer ring beingprovided with an outer raceway track of mono-hyperboloid of revolutionabout said axis; said inner raceway track and said outer raceway trackbeing oppositely faced with each other to form a raceway whose diameteris larger at one end than at the other end; the center axes of saidintermediate rotation bodies with a cylindrical or conical rollingsurface being arranged in a circumferential direction of said raceway atan angle to a cross section including said axis, and the surface of saidintermediate rotation bodies being arranged so as to come into linearcontact with said inner raceway track and said outer raceway track; saidinner ring or said outer ring rotating only in such a given direction asto roll said intermediate rotation bodies along said inner raceway trackin said one-axis direction toward a small-dia. end of said raceway; saidinner ring or said outer ring being provided with a ringlike portionwhich brings to a stop movements of said intermediate rotation bodies insaid axial direction, when said inner ring or said outer ring is rotatedin said given direction; said two single units being arranged so as toface each other in said one-axis direction; said energizing means beingarranged between said inner rings or said outer rings faced each otherin said one-axis direction, to energize said inner rings or said outerrings in said axial direction so as to narrow down the spacing of saidraceway tracks; and said outer rings or said inner rings which are notenergized by said energizing means being stationary so as not todisplace in said axial direction.